Modified nitrocellulose particles

ABSTRACT

Plastisol nitrocellulose having finely divided solids such as ballistic modifiers uniformly distributed therethrough is made by dispersing the solids in a solvent suitable for making a lacquer of nitrocellulose prior to the mixing of the solvent with the nitrocellulose in order to make the lacquer.

United States Patent 1 1 Liggett et a1.

1 1 MODIFIED NITROCELLULOSE PARTICLES [75] Inventors: Thomas Liggett, Indian Head;

Gregory C. Cox, Marlow Heights, both of Md.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Jan. 17,1974

1211 Appl. No.1 434,467

[52] ES. C1 260/220, 149/96, 149/100, 260/223, 264/3 E [51] Int. Cl. C06b 19/02, C08b 21/02 [58] Field of Search 260/223, 220; 149/96, 100; 264/3 E {56] References Cited U N ITED STATES PATENTS 1,161.630 11/1941 Regestein ..260/223 Mar. 25, 1975 Primary ExaminerRonald W. Griffin Arlorney, Agent, or Firm-R. S. Sciascia; J. A. Cooke; M. P. Perrone [57] ABSTRACT Plastisol nitrocellulose having finely divided solids such as ballistic modifiers uniformly distributed therethrough is made by dispersing the solids in a solvent suitable for making a lacquer of nitrocellulose prior to the mixing of the solvent with the nitrocellulose in order to make the lacquer.

11 Claims, N0 Drawings MODIFIED NITROCELLULOSE PARTICLES BACKGROUND OF THE INVENTION This invention relates to a method of modifying explosive or propellant compositions and more particularly to a method of modifying plastisol nitrocellulose having finely divided solids uniformly distributed therethrough and the resultant product.

In a propellant or explosive composition, many components are usually required to impart desired properties to the composition. The more effective composi tions have their components uniformly distributed therethrough. However, uniformity is difficult to obtain especially in the nitrocellulose based propellants or explosives. Uniformity leads to even burning of the propellant or explosive, and more efficient use of the components in the propellant or explosive. It is known that particles of plastisol nitrocellulose are easily distributed in a propellant or explosive. But this knowledge has not led to a uniform distribution of other components.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a method for making a propellant or explosive having components uniformly distributed therethrough. It is also an object of this invention to provide a method for making a propellant or explosive which burns evenly. it is a further object of this invention to provide a method for making a propellant or explosive which uses its material efficiently.

It is a still further object of this invention to provide a component for a propellant or explosive composition which burns uniformly.

These and other objects of inventions are met by providing a method for uniformly dispersing finely divided solids in a solvent for nitrocellulose and making a nitrocellulose lacquer with that solvent having the finely divided particles dispersed therein by mixing the nitrocellulose and the solvent. The lacquer is then subjected to highshear mixing and nitrocellulose particles having finely divided solids distributed therethrough are recovered. The resultant product is a plastisol nitrocellulose having solids uniformly distributed therethrough.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Plastisol nitrocellulose refers to a small particle nitrocellulose. These small particles of nitrocellulose are used either by themselves or in combination with other materials to make propellants or explosives. Methods of making small particles of nitrocellulose are disclosed in U.S. Pat. No. 2,915,519 to Stewart et a1, U.S. Pat. No. 2,931,801 to Sloan et al and U.S. Pat. No. 3.671.515 to Cox et al the disclosure of each of these patents being incorporated by reference. These small particles disperse readily in propellants or explosives. It is now known by virtue of this invention that other propellant or explosive components are dispersible uniformly in plastisol nitrocellulose. The plastisol nitrocellulose having the other components uniformly dispersed therein is still uniformly dispersible in a propellant or explosive. It follows that the components dis persed in the nitrocellulose particles are also uniformly dispersed in propellants or explosives when the nitrocellulose particles are uniformly dispersed in propellants or explosives.

To disperse a finely divided solid in a plastisol nitrocellulose or a nitrocellulose particle requires that the solid be dispersible in a solvent for the nitrocellulose, and nonreactive and insoluble in the solvent for nitrocellulose. The nitrocellulose may contain up to about 30% solids based on the weight of nitrocellulose. A more suitable amount of solids is about 1% to 25% by weight of nitrocellulose. Most suitably the solid content is 5 to 15% by weight of nitrocellulose. The solvent for nitrocellulose must also be compatible with the solid. If the solid is not dispersible in the solvent, it may be treated so long as the treatment is compatible with the other propellant or explosive components. Suitable solvents for the nitrocellulose include those listed in U.S. Pat. No. 3,671,515 to Cox et al the disclosure ofwhich is incorporated herein by reference. Such solvents include but are not limited to lower alkyl alcohols, ke tones, esters, and solvent mixtures. However, a preferred solvent for the nitrocellulose is nitroniethane. Suitable solids are those listed in U.S. Pat. No. 3,022,149 to Cramer incorporated herein by reference including but not limited to carbon black, metals, and metallic oxides. Other suitable solids are listed in U.S. Pat. No. 3,088,858 to Camp incorporated herein by reference.

A certain size range between the solids and the nitrocellulose is required. The particle size of nitrocellulose ranges from about one to about microns. A more suitable size range is about 5 to 50 microns. The most suitable size range is 9 to 12 microns. With respect to the finely divided solid, the size is required to be substantially smaller than the nitrocellulose particle. The solid ranges up to 10% of the size of the nitrocellulose particle and suitably 1 to 5% and even more suitably 1% to 3%. Also solids can be less than 1% of the particle size. Solids to be incorporated in the lacquer by the method of this invention comprise up to 30 percent by weight of nitrocellulose with l to 25% being more suitable. Most suitable amounts of solid are 5l5%. The solids are compatible with nitrocellulose.

To carry out the method, the solids are dispersed in a solvent for nitrocellulose which neither reacts with nor has an adverse effect on the solids. Solvents are selected based on the solid desired to be incorporated in the nitrocellulose. The solvent for nitrocellulose and the solid must be mutually insoluble and nonreactive. The solid must also be compatible with nitrocellulose. The solvent for nitrocellulose with the solid dispersed therein is then added to nitrocellulose in order to form a lacquer. The nitrocellulose is water or alcohol wet when it is mixed with the solvent to form the lacquer. Also the solid can be treated to protect it from the solvent. This mixing is carried out at a temperaturc'of from 100 to F although other temperatures are operable. This process is similar to the processes disclosed in the above-referenced patents especially U.S. Pat. No. 3,671,515 to Cox et al. 'The improvement is found in the incorporation of the solids in the solvent before it is used to form the lacquer. The solvent-having the solids dispersed therein and the nitrocellulose are then mixed together. The solvent is used in an amount sufficient to dissolve the nitrocellulose.

Having generally described the invention the following examples are given for purposes of illustration. It will be understood that the invention is not limited to these examples, but is susceptible to different modifications that will be recognized by one of ordinary skill in the art.

EXAMPLE 1 About 0.8 pound of carbon black having a particle size of about 0.5 micron is slurried in 40 pounds of nitromethane. The slurry and 0.11 pounds of ethyl centralite are added to an agitated gallon reactor. Agitation is commenced and the contents are heated to 1 F. Water wet nitrocellulose (2.2 pounds, on a dry basis) (12.6%N, moisture) is then added to the reactor maintaining the temperature at 1 10 F. Agitation is continued until all of the nitrocellulose is dissolved (about 2 hours). Twenty-two pounds of emulsion water in a tank are heated to 140 F as were 800 pounds of drown water to 120 F. The lacquer and emulsion water are then fed to a Gifford-Wood 2-inch Pipe Line Mixer emulsifier unit via concentric tubes wherein the openings of the tubes terminate in the area of (about onefourth inch from) emulsifying action so that the two liquids are mixed and substantially simultaneously subjected to emulsifying action. After passing through the high shear emulsifying action, the emulsion is discharged into the preheated drown water and agitated. The nitrocellulose particles are then separated by centrifugal action. The average particle size of the nitrocellulose is determined to be 1 1.7 microns. The particles of nitrocellulose have carbon black uniformly distributed therethrough.

EXAMPLE 2 EXAMPLE 3 The same procedure used in Example 1 is employed except that 1 pound of carbon black having a particle size of 1 micron is used, 7 pounds of 12.2% N nitrocel lulose. 40 pounds of nitromethane and 0.35 pounds of ethyl ccntralite are used. Furthermore, the emulsion water and drown water are only heated to 1 10 F. The

average particle size of nitrocellulose is determined to v be 12.2 microns.

A similar procedure as employed in Examples l-3 using 110% N containing nitrocellulose results in nitrocellulose having an average particle size of 8.5 microns.

The recovered nitrocellulose has carbon black distributed uniformly therethrough.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that. within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a method for making plastisol nitrocellulose comprising a. mixing a nitrocellulose and a solvent for nitrocellw lose to form a nitrocellulose lacquer;

b. mixing the lacquer with water to form a mixture;

c. emulsifying the mixture under high shear mixing conditions;

d. recovering the nitrocellulose in particle form the improvement which comprises: dispersing a finely divided solid in the solvent prior to mixing the solvent with nitrocellulose; wherein the solid is l. dispersible in the solvent, 2. compatible with nitrocellulose, 3. insoluble in the solvent, 4. non reactive with the solvent and 5. present in an amount up to about 30% by weight of the nitrocellulose to distribute the solid therein.

2. The method of claim 1 wherein the solid is a ballistic modifier.

3. The method of claim 1 wherein the solid is colloidal carbon black of substantially smaller size than the nitrocellulose in particle form.

4. The method of claim 3 wherein the solvent is nitromethane.

5. The method of claim 4 wherein the particle size of the nitrocellulose is from 1 to microns.

6. The method of claim 2 wherein the solid has a particle size of up to 10% of the particle size of the nitrocellulose.

7. The method of claim 6 wherein the particle size of the nitrocellulose is 5 to 50 microns.

8. A plastisol nitrocellulose particle having finely di' vided solids uniformly distributed therethrough wherein:

the solids are compatible with the nitrocellulose particle;

the solids comprise up to 30% by weight of the nitrocellulose particle'. and the solids have a particle size range up to 10% of the size of the plastisol nitrocellulose particle. 9. The particle of claim 8 wherein the solid has a size range 1% to 5% of the size of the nitrocellulose 10. The particle of claim 9 wherein the solid comprises l% to 25% by weight of the particle.

11. The particle of claim 10 wherein the solid is col- 

1. IN A METHOD FOR MAKING PLASTISOL NITROCELLULOSE COMPRISING A. MIXING A NITROCELLULOSE AND A SOLVENT FOR NITROCELLULOSE TO FORM A NITROCELLULOSE LACQUER; B. MIXING THE LACQUER WITH WATER TO FORM A MIXTURE; C. EMULSIFYING THE MIXTURE UNDER HIGH SHEAR MIXING CONDITIONS; D. RECOVERING THE NITROCELLULOSE IN PARTICLE FORM THE IMPROVEMENT WHICH COMPRISES: DISPERSING A FINELY DIVIDED SOLID IN THE SOLVENT PRIOR TO MIXING THE SOLVENT WITH NITROCELLULOSE; WHEREIN THE SOLID IS
 1. DISPERSIBLE IN THE SOLVENT,
 2. COMPATIBLE WITH NITROCELLULOSE,
 2. compatible with nitrocellulose,
 2. The method of claim 1 wherein the solid is a ballistic modifier.
 3. The method of claim 1 wherein the solid is colloidal carbon black of substantially smaller size than the nitrocellulose in particle form.
 3. insoluble in the solvent,
 3. INSOLUBLE IN THE SOLVENT,
 4. NON REACTIVE WITH THE SOLVENT AND
 4. non reactive with the solvent and
 4. The method of claim 3 wherein the solvent is nitromethane.
 5. The method of claim 4 wherein the particle size of the nitrocellulose is from 1 to 100 microns.
 5. present in an amount up to about 30% by weight of the nitrocellulose to distribute the solid therein.
 5. PRESENT IN AN AMOUNT UP TO ABOUT 30% BY WEIGHT OF THE NITROCELLULOSE TO DISTRIBUTE THE SOLID THEREIN.
 6. The method of claim 2 wherein the solid has a particle size of up to 10% of the particle size of the nitrocellulose.
 7. The method of claim 6 wherein the particle size of the nitrocellulose is 5 to 50 microns.
 8. A PLASTISOL NITROCELLULOSE PARTICLE HAVING FINELY DIVIDED SOLIDS UNIFORMLY DISTRIBUTED THERETHROUGH WHEREIN: THE SOLIDS ARE COMPATIBLE WITH THE NITROCELLULOSE PARTICLE; THE SOLIDS COMPRISE UP TO 30% BY WEIGHT OF THE NITROCELLULOSE PARTICLE; AND THE SOLIDS HAVE A PARTICLE SIZE RANGE UP TO 10% OF THE SIZE OF THE PLASTISOL NITROCELLULOSE PARTICLE.
 9. The particle of claim 8 wherein the solid has a size range 1% to 5% of the size of the nitrocellulose
 10. The particle of claim 9 wherein the solid comprises 1% to 25% by weight of the particle.
 11. The particle of claim 10 wherein the solid is colloidal carbon black. 